Something simple, with 4 knobs: LF pass freq and gain, and HF pass freq and gain.
I know Emotiva doesn't like knobs. So some kind of intuitive LCD display for setting the LF and HF pass and gain.
You would connect this downstream of the preamp, for crystal-clear signal direction to your main speakers and subwoofers.
Or go crazy: make it a 3-band active crossover (low, mids, highs), so you could add both subs, and exotic ribbon tweeters for the super highs in your music.
(HINT HINT Emotiva: how about making a small-box ribbon tweeter, that could sit on top of the XRT-5.2 Towers for the super-highs?)
Old-School Hi-Fi Junkie: Pioneer PLC-590, Infinity Black Widow, GAS Sleeping Beauty GAS Thaedra Preamp Sony CDP-X7ESD CD player Emotiva XDA-1 DAC Sansui TU-719 Tuner Emotiva XPA-2 Power Amp Magnepan MMG Speakers Polk Subs